Functions > Image Processing > Image Manipulation > Thresholding
  
Thresholding
• threshold(M, thresh)—Returns the matrix M with every element below thresh set to thresh. If thresh is negative, every element above −thresh is set to −thresh.
Thresholding can be used to remove background features (or noise) in an image or to shift its intensity spectrum.
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This function can be used in one of three ways:
• When thresh is zero, all elements are set to zero.
• When thresh is positive, elements of M less than thresh are set to zero; otherwise they retain their original value.
• When thresh is negative, elements of M greater than the absolute value of thresh are set to zero; otherwise they retain their original value.
Arguments
• M is an image matrix.
• thresh a real number.